1. Field of the Invention
This invention relates to laser apparatuses, and, more particularly, to a laser apparatus for assessing alignment of a plurality of spaced-apart structural elements.
2. Description of the Related Art
Laser alignment systems include a laser for generating a laser beam and a light-sensitive target cell. The target cell is operative to generate electrical signals that identify the location of the center of energy of the laser beam impinging on the target cell. The light-sensitive target cell typically is mounted in a housing, and the housing is mounted to a structural element that must be aligned to another structural element or to some pre-established frame of reference. The laser is fixedly mounted to the other structural member or in proximity to the frame of reference. The laser then directs a beam on the light-sensitive target cell, and the target cell produces signals to identify both the position and the angular alignment of the target cell relative to the laser beam. Adjustments can be made to the structure on which the target is mounted so that the center of the target cell is positioned on the center of energy of the laser beam and so that the target cell is aligned substantially perpendicular to the laser beam.
Some prior art laser alignment systems employ a penta-prism. The penta-prism receives an input laser beam and permits a plurality of internal reflections. As a result of these reflections, an output laser beam emerges from the penta-prism at precisely right angles to the input laser beam. The penta-prism then may be rotated about the axis defined by the input laser beam. As a result, the output laser beam will sweep a perfectly flat laser plane. Systems of this type typically are used with a plurality of light-sensitive target cells mounted to a plurality of structural elements that require alignment relative to the laser reference plane. A system of this type is shown in U.S. Pat. No. 4,297,031.
U.S. Pat. No. 5,307,368 discloses a laser apparatus for generating up to three mutually perpendicular laser planes. In a first embodiment shown in U.S. Pat. No. 5,307,368 the apparatus is formed with three separate laser sources, and three separate beam adjustment means. Hamar Laser Instruments, Inc. manufactures and sells a laser apparatus, Model No. 723, formed in accordance with the first embodiment of U.S. Pat. No. 5,307,368. Hamar Model No. 723 is very effective and precise, but also is relatively expensive. The cost of the Hamar Model No. 723 laser apparatus can be reduced by using a single laser source, rather than three separate laser sources, and U.S. Pat. No. 5,307,368 shows three embodiments which utilize a single laser source to simultaneously produce three mutually perpendicular planes. Specifically, beam splitters and/or fiber optic elements are used to split a single laser beam into three separate beams. However, for each of these embodiments, beam adjustment means are provided for each of the resulting split laser beams to achieve mutual perpendicularity. Unfortunately, the costs of the beam adjustment means also are relatively high.
It is an object of the subject invention to provide a laser apparatus which utilizes a single laser source to simultaneously generate a plurality of laser planes.
It is also an object of the subject invention to provide a laser apparatus without beam adjustment means for simultaneously generating a plurality of laser planes arranged to be generally mutually perpendicular.